The present invention relates generally to the field of photography, and, more particularly, to an apparatus for altering the field frame of an image in the viewfinder of a camera, and to a method of using the apparatus.
A typical camera includes a viewfinder through which a photographer can view an image to be photographed. The photographer""s view through the viewfinder is essentially a preview of the image that will be captured by the camera. Ideally, the field frame of the viewfinder image should accurately represent the format of the image to be captured. In other words, given that a photographic image has finite boundaries (e.g., a rectangle of a particular height and width), the photographer should be able to discern by looking through the viewfinder which objects will fall within those boundaries and which objects will fall without.
Various cameras support more than one format. For example, Advanced Photo System (xe2x80x9cAPSxe2x80x9d) cameras permit a photographer to select a format from among rectangular shapes having various aspect ratios. Some 35 mm cameras have a normal mode and a xe2x80x9cpanoramaxe2x80x9d mode, thus offering a photographer a selection of two aspect ratios. Certain xe2x80x9cspecial usexe2x80x9d or xe2x80x9cnoveltyxe2x80x9d cameras allow an image to be framed in a shape such as a circle or a heart at the election of the photographer. A viewfinder, however, is generally a fixed optical system, so the image in the viewfinder has boundaries determined by the fixed dimensions of the system. In a multi-format camera, it is desirable to provide a mechanism to alter the field frame in the viewfinder to correspond to a selected format.
One device for altering the field frame in a viewfinder is a mask having an aperture with a shape corresponding to a selected format. The mask is placed in the viewfinder""s optical path when the format corresponding to its aperture""s shape is selected, and is removed from the optical path when that format is not selected. The use of a mask in a viewfinder is generally known. See, e.g., U.S. Pat. Nos. 2,542,939; 5,430,517; 5,530,510; 5,555,058; 5,587,755; 5,689,743; 5,623,324; and 5,828,914. Using a mask in some cameras, however, has drawbacks: first, the mask requires an apparatus to move the mask into and out of the viewfinder""s optical path, and, second, the mask must be stored when it is not in use. Both the mask-moving apparatus and the storage of the mask require space, which requires that the camera be made large enough to provide the space. Moreover, the apparatus may increase the cost and complexity of the camera. Increased cost and size are particularly undesirable in certain types of cameras, such as single-use cameras, whose principal advantage is that they are small and inexpensive.
In view of the foregoing, there is a need for a device that overcomes the drawbacks of the prior art.
The present invention is directed to a foldable mask, and a mechanism for moving the foldable mask into and out the optical path of a device, such as a camera viewfinder.
A mask having a hinge is provided. The mask is foldable by way of the hinge, which is preferably a living hinge formed in the material of which the mask is made. The mask is located in the vicinity of the optical path in which it is to be placed, which, in a preferred embodiment, is the optical path in a camera viewfinder. The mask is movable between two positions, a first (unfolded) position where it is in said optical path, and a second (folded) position where it is not in said optical path. A power transmission mechanism moves the mask from the first position to the second position. As the mask moves, the locus of motion of the mask is restricted to rotational motion on one side of the mask and linear motion on the other side. This combination of motion restrictions causes the mask to fold at the hinge as it moves from the first position to the second position. The folded mask stores compactly alongside the viewfinder while it is not in use.
In a preferred embodiment of the invention, the mask is made of a light-intercepting material having an aperture. The shape of the aperture corresponds to the shape of a field frame to be used for an image. For example, in many cameras a xe2x80x9cpanoramaxe2x80x9d picture format is characterized by a rectangular shape that is about twice as wide as it is high. In such a case, a mask having an elongated rectangular aperture can be placed in between the lenses of a two-lens viewfinder perpendicular to the optical path, thereby allowing a photographer to see the viewfinder image in a panorama format.
In another preferred embodiment, the mask is used in the viewfinder of a multi-format camera having a format-selector switch. In such an embodiment, a user can operate the power transmission mechanism, by way of the format-selector switch, to move the mask between its two positions. For example, the camera may support two formats, one corresponding to the natural shape of the viewfinder, and the other corresponding to the aperture of the mask. A photographer uses the format selector switch to move the mask into, or out of, the viewfinder""s optical path, depending upon which format the photographer wishes to use. The multi-format camera is preferably an APS camera in which the switch is also coupled to a format-encoding device. The format-encoding device encodes a film to indicate which format has been selected for an exposed frame. Preferably, the switch operates both the mask and the format-encoding device, so that the format to be encoded will be set at the same time that the photographer selects the viewfinder field frame.
Other features of the invention are described below.